Mirex and chlordecone are two separate, but chemically similar, manufactured insecticides that do not occur naturally in the environment. Mirex is a white crystalline solid, and chlordecone is a tan-white crystalline solid. Both chemicals are odorless.

Mirex and chlordecone have not been manufactured or used in the United States since 1978. Mirex was used to control fire ants, and as a flame retardant in plastics, rubber, paint, paper, and electrical goods from 1959 to 1972. Chlordecone was used as an insecticide on tobacco, ornamental shrubs, bananas, and citrus trees, and in ant and roach traps. Mirex was sold as a flame retardant under the trade name Dechlorane, and chlordecone was also known as Kepone.



Structural diagrams: National Institutes of Health

Fate & Transport

Mirex and chlordecone break down slowly in the environment, and they may stay for years in soil and water. They do not evaporate to any great extent from surface water or surface soil. Mirex and chlordecone do not dissolve easily in water, but they easily stick to soil and sediment particles. They are not likely to travel far through the soil and into underground water. They can build up in fish or other organisms that live in contaminated water or that eat other contaminated animals.

Exposure Pathways

Touching or ingesting contaminated soil near hazardous waste sites.

Ingesting contaminated fish or other animals living near hazardous waste sites.

Nursing infants of mothers living near hazardous waste sites may be exposed to mirex through their mothers' milk.

Drinking water or breathing air is not likely to cause exposure because these compounds do not easily dissolve in water or evaporate.

Health Effects

We do not know how mirex affects the health of people. Workers who were exposed to high levels of chlordecone over a long period (more than one year) showed harmful effects on the nervous system, skin, liver, and male reproductive system. These workers were probably exposed mainly through touching chlordecone, although they may have inhaled or ingested some as well.

Animal studies with chlordecone have shown effects similar to those seen in people, as well as harmful kidney effects, developmental effects, and effects on the ability of females to reproduce. We do not know if these last three effects also occur in people. Animal studies have shown that ingesting high levels of mirex can harm the stomach, intestine, liver, kidneys, eyes, thyroid, and nervous and reproductive systems.

The Department of Health and Human Services (DHHS) determined that mirex and chlordecone may reasonably be anticipated to be carcinogens. There are no studies available on whether mirex and chlordecone are carcinogenic in people. However, studies in mice and rats have shown that ingesting mirex and chlordecone can cause liver, adrenal gland, and kidney tumors.

Information excerpted from:

Toxicological Profile for Mirex and Chlordecone, 1995

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services